Use BaseDbObjectTestCase in AddressScope UT
Use BaseDbObjectTestCase in AddressScope UT

AddressScopeDbObjectTestCase class is using _BaseObjectTestCase class
which doesn't contain all the unit test cases for Oslo-Versioned
classes. This patch replace that class.

Partially-Implements: blueprint adopt-oslo-versioned-objects-for-db

Change-Id: I180046743471487a9f9a6e53ae0f2fd09afdf123

eayunstack/neutron,openstack/neutron,mahak/neutron,sebrandon1/neutron,noironetworks/neutron,huntxu/neutron,noironetworks/neutron,cloudbase/neutron,openstack/neutron,eayunstack/neutron,mahak/neutron,huntxu/neutron,mahak/neutron,sebrandon1/neutron,openstack/neutron,cloudbase/neutron